Apparatus for eliminating cohesion between overlying plies of plastic film material

ABSTRACT

Adhesion between the overlying plies of a flattened tubular web of plastic film material is eliminated by drawing the web lengthwise past a rod which is supported in a position transverse to the web and is interposed between its plies.

United States Patent [191 Dahlberg Apr. 9, 1974 1 APPARATUS FORELIMINATING COHESION BETWEEN OVERLYING PLIES OF PLASTIC FILM MATERIAL[75] Inventor: Thomas J. Dahlberg, Wyoming,

Minn.

[73] Assignee: Possis Corporation, Minneapolis,

Minn.

22 Filed: May 11, 1973 211 Appll No.1 359,620

Related US. Application Data [62] Division of Ser. No. 161,669, July 12,1971.

[52] US. Cl. .L 53/384 [51] Int. Cl B65b 43/26 [58] Field of Search53/384, 241, 256

[56] References Cited UNITED STATES PATENTS 3,308,601 3/1967 Masters53/241 X 3,287,881 ll/l966 Jelling et a1 53/241 X 3,360,901 l/l968 Gallo53/384 X Primary Examiner-Travis S. McGehee [5 7] ABSTRACT Adhesionbetween the overlying plies of a flattened tubular web of plastic filmmaterial is eliminated by drawing the web lengthwise past a rod which issupported in a position transverse'to the web and is interposed betweenits plies.

2 Claims, 2 Drawing Figures This application is a division of mycopending allowed application, Ser. No. 161,669, filed July 12, 1971.

This invention concerns the problem of objectionable cohesion betweenoverlying plies or sheets of thin plastic material.

The specific problem solved by the invention was encountered in theoperation of a machine for wrapping, en masse, large numbers of looseobjects such as boxes, cans and variouscontainers, in plastic film.Usually the objects to be wrapped are piled on a pallet to facilitatetransporting them from place to place. As such, they are considered apalletized load. These palletized loads are successively brought to themachine, which then draws gusseted tubular plastic stock down over theload.

The gusseted tubular stock is supplied in rolls from which the machinepulls it as a flattened web and feeds it downwardly towards the load inposition to be wrapped. A cutoff knife severs the web at a distance fromits end such that the severed length is long enough to encompass theload, but the knife does not act until heat sealing devices securecertain of the overlying plies of the web to one another to at leastpartially close the tubular web. Since the cutoff knife is locatedupstream of the location at which the heat sealing devices work, thepartial (or complete) closure contacts the top of the load to limit theextent the tubular stock can be pulled down onto the load, and therebyprecludes having the enwrapment pulled away from the upper portion ofthe load during the subsequent heat shrink shaped memberhaving a slot inits bottom through which the flattened tubular web is drawn; and

FIG. 2 is a cross sectional view taken on the line 2-2 of FIG. 1.

Referring now more particularly to the drawing, it will be noted that around rod 5 is inserted between each outer side panel 6 of the gussetedtubular web 7 operation by which the plastic film is shrunk intointimate contact with the load.

To facilitate opening the tubular web preparatory to having it drawndown over the load, the web is not severed until tube opening devicesact upon the end of the web. The tube opening devices include suctioncups which approach the pendent length of the tubular gusseted stockfrom opposite sides of the machine and attach themselves to the sidepanels of the web just before the cutoff knife acts. By means of thesuction cups, which are now moved outwardly, the side panels are drawnaway from one another to thereby open the gussets and form the web ofthe tubular stock into a tube. This is the way the machine should work,and it does if nothing interferes with separation of the side panels.But the inevitable cohesion between overlying plies of thin plasticmaterial whether caused by static electricity or otherwise made itdifficult for the suction cups to reliably open the tubular stock.

Some way had to be found to eliminate the cohesion between the sidepanels and between the side panels and the gussets therebetween. Thisinvention achieves that objective by a method which entails drawing thegusseted flattened web of plastic film material lengthwise past rodswhich are positioned transversely of the web, between the plies thereof.

The accompanying drawing illustrates one way in which the method of thisinvention can be practiced, and in which:

FIG. 1 is a more or less diagrammatic perspective view showing how therods are supported in a channeland its inwardly adjacent gussets 8. Toenable such insertion holes are simply cut into. the web at thejunctions of the side panels and the gussets. The rods are inside-by-side relationship and extend transversely of the web.Necessarily, the rods are located at a point in the path of the web 7between the roll from which the web is drawn and the heat sealingdevice. At that point, the web travels upwardly as indicated by thearrow in FIG. 1 and, accordingly, the rods are horizontally disposed.

One convenient way of supporting the rods 5 and also of assuring contactbetween the rods and the side panels and gussets, is to have the webpass through an elongated slot 9 in the bottom of an upwardly facingchannel member 10 that is fixedly mounted on the frame of the machine.The width of the slot must be less than the diameter of the rods 5 tokeep the rods from falling through the slot, and the inside width of thechannel should be a bit greater than twice the diameter of the rods, sothat the rods can float up and down in the channel as the web is drawnupwardly past them.

Though the diameter of the rods ,5 is not critical, inch rods have beenfound to be quite satisfactory. Also, the material of which the rodsaremade is not critical, but metal rods are perhaps preferable.

Justwhy the passage of the web past the rods but, of course, in contactwith them eliminates the objectionable cohesion, is not known. But inany event, all cohesion problems in the operation of the aforesaidwrapping machine have been overcome by the incorporation of these rodsinto the machine.

From the foregoing description, together with the accompanying drawing,it will be readily apparent to those skilled in the art that thisinvention is useful for the elimination of cohesion between the plies ofgusseted as well as non-gusseted plastic film material in flattenedtubular condition; and that the invention can be practiced in apparatusother than as herein disclosed for purposes of illustration.

The invention is defined by the following claims.

I claim:

l. A device for eliminating cohesion between plies of a gussetedflattened tubular web of plastic film material as it'travels upwardlyalong a defined path, comprising:

A. an elongated metal bar disposed horizontally in the path of theupwardly traveling gusseted plastic web, said bar having alongitudinally extending slot long enough to accommodate the width ofthe gusseted plastic web so that said web can be drawn upwardly throughthe slot;

B. a pair of unconnected separate metal rods loosely lying on said bar,the cross sectional dimension of each of said rods being greater thanthe width of said slot, and each rod being long enough to spansubstantially the entire width of the side panels of the plastic web, sothat as the gusseted plastic web travels upwardly through said slot withone of said rods between each of its side panels and its adjacentgussets,

3 4 the rods will not drop through the slot but will rods are confinedin side-by-side relation. separate the side panels of the web from theirad- The Cohesion eliminating device of claim 1 jacent gussets; and C.upwardly projecting barriers on said bar at opposite sides of the slottherein and between which said 5 wherein each of said rods is round incross section.

1. A device for eliminating cohesion between plies of a gusseted flattened tubular web of plastic film material as it travels upwardly along a defined path, comprising: A. an elongated metal bar disposed horizontally in the path of the upwardly traveling gusseted plastic web, said bar having a longitudinally extending slot long enough to accommodate the width of the gusseted plastic web so that said web can be drawn upwardly through the slot; B. a pair of unconnected separate metal rods loosely lying on said bar, the cross sectional dimension of each of said rods being greater than the width of said slot, and each rod being long enough to span substantially the entire width of the side panels of the plastic web, so that as the gusseted plastic web travels upwardly through said slot with one of said rods between each of its side panels and its adjacent gussets, the rods will not drop through the slot but will separate the side panels of the web from their adjacent gussets; and C. upwardly projecting barriers on said bar at opposite sides of the slot therein and between which said rods are confined in side-by-side relation.
 2. The cohesion eliminating device of claim 1, wherein each of said rods is round in cross section. 